/*
 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 1999-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: NamespaceSupport2.java,v 1.3 2005/09/28 13:49:20 pvedula Exp $
 */
package com.sun.org.apache.xml.internal.utils;

import java.util.EmptyStackException;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Vector;

/**
 * Encapsulate Namespace tracking logic for use by SAX drivers.
 *
 * <p>This class is an attempt to rewrite the SAX NamespaceSupport
 * "helper" class for improved efficiency. It can be used to track the
 * namespace declarations currently in scope, providing lookup
 * routines to map prefixes to URIs and vice versa.</p>
 *
 * <p>ISSUE: For testing purposes, I've extended NamespaceSupport even
 * though I'm completely reasserting all behaviors and fields.
 * Wasteful.... But SAX did not put an interface under that object and
 * we seem to have written that SAX class into our APIs... and I don't
 * want to argue with it right now. </p>
 *
 * @see org.xml.sax.helpers.NamespaceSupport
 */
public class NamespaceSupport2
    extends org.xml.sax.helpers.NamespaceSupport {
  ////////////////////////////////////////////////////////////////////
  // Internal state.
  ////////////////////////////////////////////////////////////////////

  private Context2 currentContext; // Current point on the double-linked stack

  ////////////////////////////////////////////////////////////////////
  // Constants.
  ////////////////////////////////////////////////////////////////////


  /**
   * The XML Namespace as a constant.
   *
   * <p>This is the Namespace URI that is automatically mapped
   * to the "xml" prefix.</p>
   */
  public final static String XMLNS =
      "http://www.w3.org/XML/1998/namespace";

  ////////////////////////////////////////////////////////////////////
  // Constructor.
  ////////////////////////////////////////////////////////////////////


  /**
   * Create a new Namespace support object.
   */
  public NamespaceSupport2() {
    reset();
  }

  ////////////////////////////////////////////////////////////////////
  // Context management.
  ////////////////////////////////////////////////////////////////////


  /**
   * Reset this Namespace support object for reuse.
   *
   * <p>It is necessary to invoke this method before reusing the
   * Namespace support object for a new session.</p>
   */
  public void reset() {
    // Discarding the whole stack doesn't save us a lot versus
    // creating a new NamespaceSupport. Do we care, or should we
    // change this to just reset the root context?
    currentContext = new Context2(null);
    currentContext.declarePrefix("xml", XMLNS);
  }


  /**
   * Start a new Namespace context.
   *
   * <p>Normally, you should push a new context at the beginning
   * of each XML element: the new context will automatically inherit
   * the declarations of its parent context, but it will also keep
   * track of which declarations were made within this context.</p>
   *
   * <p>The Namespace support object always starts with a base context
   * already in force: in this context, only the "xml" prefix is
   * declared.</p>
   *
   * @see #popContext
   */
  public void pushContext() {
    // JJK: Context has a parent pointer.
    // That means we don't need a stack to pop.
    // We may want to retain for reuse, but that can be done via
    // a child pointer.

    Context2 parentContext = currentContext;
    currentContext = parentContext.getChild();
    if (currentContext == null) {
      currentContext = new Context2(parentContext);
    } else {
      // JJK: This will wipe out any leftover data
      // if we're reusing a previously allocated Context.
      currentContext.setParent(parentContext);
    }
  }


  /**
   * Revert to the previous Namespace context.
   *
   * <p>Normally, you should pop the context at the end of each
   * XML element.  After popping the context, all Namespace prefix
   * mappings that were previously in force are restored.</p>
   *
   * <p>You must not attempt to declare additional Namespace
   * prefixes after popping a context, unless you push another
   * context first.</p>
   *
   * @see #pushContext
   */
  public void popContext() {
    Context2 parentContext = currentContext.getParent();
    if (parentContext == null) {
      throw new EmptyStackException();
    } else {
      currentContext = parentContext;
    }
  }

  ////////////////////////////////////////////////////////////////////
  // Operations within a context.
  ////////////////////////////////////////////////////////////////////


  /**
   * Declare a Namespace prefix.
   *
   * <p>This method declares a prefix in the current Namespace
   * context; the prefix will remain in force until this context
   * is popped, unless it is shadowed in a descendant context.</p>
   *
   * <p>To declare a default Namespace, use the empty string.  The
   * prefix must not be "xml" or "xmlns".</p>
   *
   * <p>Note that you must <em>not</em> declare a prefix after
   * you've pushed and popped another Namespace.</p>
   *
   * <p>Note that there is an asymmetry in this library: while {@link
   * #getPrefix getPrefix} will not return the default "" prefix,
   * even if you have declared one; to check for a default prefix,
   * you have to look it up explicitly using {@link #getURI getURI}.
   * This asymmetry exists to make it easier to look up prefixes
   * for attribute names, where the default prefix is not allowed.</p>
   *
   * @param prefix The prefix to declare, or null for the empty string.
   * @param uri The Namespace URI to associate with the prefix.
   * @return true if the prefix was legal, false otherwise
   * @see #processName
   * @see #getURI
   * @see #getPrefix
   */
  public boolean declarePrefix(String prefix, String uri) {
    if (prefix.equals("xml") || prefix.equals("xmlns")) {
      return false;
    } else {
      currentContext.declarePrefix(prefix, uri);
      return true;
    }
  }


  /**
   * Process a raw XML 1.0 name.
   *
   * <p>This method processes a raw XML 1.0 name in the current
   * context by removing the prefix and looking it up among the
   * prefixes currently declared.  The return value will be the
   * array supplied by the caller, filled in as follows:</p>
   *
   * <dl>
   * <dt>parts[0]</dt>
   * <dd>The Namespace URI, or an empty string if none is
   * in use.</dd>
   * <dt>parts[1]</dt>
   * <dd>The local name (without prefix).</dd>
   * <dt>parts[2]</dt>
   * <dd>The original raw name.</dd>
   * </dl>
   *
   * <p>All of the strings in the array will be internalized.  If
   * the raw name has a prefix that has not been declared, then
   * the return value will be null.</p>
   *
   * <p>Note that attribute names are processed differently than
   * element names: an unprefixed element name will received the
   * default Namespace (if any), while an unprefixed element name
   * will not.</p>
   *
   * @param qName The raw XML 1.0 name to be processed.
   * @param parts A string array supplied by the caller, capable of holding at least three members.
   * @param isAttribute A flag indicating whether this is an attribute name (true) or an element
   * name (false).
   * @return The supplied array holding three internalized strings representing the Namespace URI
   * (or empty string), the local name, and the raw XML 1.0 name; or null if there is an undeclared
   * prefix.
   * @see #declarePrefix
   * @see java.lang.String#intern
   */
  public String[] processName(String qName, String[] parts,
      boolean isAttribute) {
    String[] name = currentContext.processName(qName, isAttribute);
    if (name == null) {
      return null;
    }

    // JJK: This recopying is required because processName may return
    // a cached result. I Don't Like It. *****
    System.arraycopy(name, 0, parts, 0, 3);
    return parts;
  }


  /**
   * Look up a prefix and get the currently-mapped Namespace URI.
   *
   * <p>This method looks up the prefix in the current context.
   * Use the empty string ("") for the default Namespace.</p>
   *
   * @param prefix The prefix to look up.
   * @return The associated Namespace URI, or null if the prefix is undeclared in this context.
   * @see #getPrefix
   * @see #getPrefixes
   */
  public String getURI(String prefix) {
    return currentContext.getURI(prefix);
  }


  /**
   * Return an enumeration of all prefixes currently declared.
   *
   * <p><strong>Note:</strong> if there is a default prefix, it will not be
   * returned in this enumeration; check for the default prefix
   * using the {@link #getURI getURI} with an argument of "".</p>
   *
   * @return An enumeration of all prefixes declared in the current context except for the empty
   * (default) prefix.
   * @see #getDeclaredPrefixes
   * @see #getURI
   */
  public Enumeration getPrefixes() {
    return currentContext.getPrefixes();
  }


  /**
   * Return one of the prefixes mapped to a Namespace URI.
   *
   * <p>If more than one prefix is currently mapped to the same
   * URI, this method will make an arbitrary selection; if you
   * want all of the prefixes, use the {@link #getPrefixes}
   * method instead.</p>
   *
   * <p><strong>Note:</strong> this will never return the empty
   * (default) prefix; to check for a default prefix, use the {@link
   * #getURI getURI} method with an argument of "".</p>
   *
   * @param uri The Namespace URI.
   * @return One of the prefixes currently mapped to the URI supplied, or null if none is mapped or
   * if the URI is assigned to the default Namespace.
   * @see #getPrefixes(java.lang.String)
   * @see #getURI
   */
  public String getPrefix(String uri) {
    return currentContext.getPrefix(uri);
  }


  /**
   * Return an enumeration of all prefixes currently declared for a URI.
   *
   * <p>This method returns prefixes mapped to a specific Namespace
   * URI.  The xml: prefix will be included.  If you want only one
   * prefix that's mapped to the Namespace URI, and you don't care
   * which one you get, use the {@link #getPrefix getPrefix}
   * method instead.</p>
   *
   * <p><strong>Note:</strong> the empty (default) prefix is
   * <em>never</em> included in this enumeration; to check for the
   * presence of a default Namespace, use the {@link #getURI getURI}
   * method with an argument of "".</p>
   *
   * @param uri The Namespace URI.
   * @return An enumeration of all prefixes declared in the current context.
   * @see #getPrefix
   * @see #getDeclaredPrefixes
   * @see #getURI
   */
  public Enumeration getPrefixes(String uri) {
    // JJK: The old code involved creating a vector, filling it
    // with all the matching prefixes, and then getting its
    // elements enumerator. Wastes storage, wastes cycles if we
    // don't actually need them all. Better to either implement
    // a specific enumerator for these prefixes... or a filter
    // around the all-prefixes enumerator, which comes out to
    // roughly the same thing.
    //
    // **** Currently a filter. That may not be most efficient
    // when I'm done restructuring storage!
    return new PrefixForUriEnumerator(this, uri, getPrefixes());
  }


  /**
   * Return an enumeration of all prefixes declared in this context.
   *
   * <p>The empty (default) prefix will be included in this
   * enumeration; note that this behaviour differs from that of
   * {@link #getPrefix} and {@link #getPrefixes}.</p>
   *
   * @return An enumeration of all prefixes declared in this context.
   * @see #getPrefixes
   * @see #getURI
   */
  public Enumeration getDeclaredPrefixes() {
    return currentContext.getDeclaredPrefixes();
  }


}

////////////////////////////////////////////////////////////////////
// Local classes.
// These were _internal_ classes... but in fact they don't have to be,
// and may be more efficient if they aren't.
////////////////////////////////////////////////////////////////////

/**
 * Implementation of Enumeration filter, wrapped
 * aroung the get-all-prefixes version of the operation. This is NOT
 * necessarily the most efficient approach; finding the URI and then asking
 * what prefixes apply to it might make much more sense.
 */
class PrefixForUriEnumerator implements Enumeration {

  private Enumeration allPrefixes;
  private String uri;
  private String lookahead = null;
  private NamespaceSupport2 nsup;

  // Kluge: Since one can't do a constructor on an
  // anonymous class (as far as I know)...
  PrefixForUriEnumerator(NamespaceSupport2 nsup, String uri, Enumeration allPrefixes) {
    this.nsup = nsup;
    this.uri = uri;
    this.allPrefixes = allPrefixes;
  }

  public boolean hasMoreElements() {
    if (lookahead != null) {
      return true;
    }

    while (allPrefixes.hasMoreElements()) {
      String prefix = (String) allPrefixes.nextElement();
      if (uri.equals(nsup.getURI(prefix))) {
        lookahead = prefix;
        return true;
      }
    }
    return false;
  }

  public Object nextElement() {
    if (hasMoreElements()) {
      String tmp = lookahead;
      lookahead = null;
      return tmp;
    } else {
      throw new java.util.NoSuchElementException();
    }
  }
}

/**
 * Internal class for a single Namespace context.
 *
 * <p>This module caches and reuses Namespace contexts, so the number allocated
 * will be equal to the element depth of the document, not to the total
 * number of elements (i.e. 5-10 rather than tens of thousands).</p>
 */
final class Context2 {

  ////////////////////////////////////////////////////////////////
  // Manefest Constants
  ////////////////////////////////////////////////////////////////

  /**
   * An empty enumeration.
   */
  private final static Enumeration EMPTY_ENUMERATION =
      new Vector().elements();

  ////////////////////////////////////////////////////////////////
  // Protected state.
  ////////////////////////////////////////////////////////////////

  Hashtable prefixTable;
  Hashtable uriTable;
  Hashtable elementNameTable;
  Hashtable attributeNameTable;
  String defaultNS = null;

  ////////////////////////////////////////////////////////////////
  // Internal state.
  ////////////////////////////////////////////////////////////////

  private Vector declarations = null;
  private boolean tablesDirty = false;
  private Context2 parent = null;
  private Context2 child = null;

  /**
   * Create a new Namespace context.
   */
  Context2(Context2 parent) {
    if (parent == null) {
      prefixTable = new Hashtable();
      uriTable = new Hashtable();
      elementNameTable = null;
      attributeNameTable = null;
    } else {
      setParent(parent);
    }
  }


  /**
   * @returns The child Namespace context object, or null if this is the last currently on the
   * chain.
   */
  Context2 getChild() {
    return child;
  }

  /**
   * @returns The parent Namespace context object, or null if this is the root.
   */
  Context2 getParent() {
    return parent;
  }

  /**
   * (Re)set the parent of this Namespace context.
   * This is separate from the c'tor because it's re-applied
   * when a Context2 is reused by push-after-pop.
   *
   * @param parent The parent Namespace context object.
   */
  void setParent(Context2 parent) {
    this.parent = parent;
    parent.child = this;        // JJK: Doubly-linked
    declarations = null;
    prefixTable = parent.prefixTable;
    uriTable = parent.uriTable;
    elementNameTable = parent.elementNameTable;
    attributeNameTable = parent.attributeNameTable;
    defaultNS = parent.defaultNS;
    tablesDirty = false;
  }


  /**
   * Declare a Namespace prefix for this context.
   *
   * @param prefix The prefix to declare.
   * @param uri The associated Namespace URI.
   * @see org.xml.sax.helpers.NamespaceSupport2#declarePrefix
   */
  void declarePrefix(String prefix, String uri) {
    // Lazy processing...
    if (!tablesDirty) {
      copyTables();
    }
    if (declarations == null) {
      declarations = new Vector();
    }

    prefix = prefix.intern();
    uri = uri.intern();
    if ("".equals(prefix)) {
      if ("".equals(uri)) {
        defaultNS = null;
      } else {
        defaultNS = uri;
      }
    } else {
      prefixTable.put(prefix, uri);
      uriTable.put(uri, prefix); // may wipe out another prefix
    }
    declarations.addElement(prefix);
  }


  /**
   * Process a raw XML 1.0 name in this context.
   *
   * @param qName The raw XML 1.0 name.
   * @param isAttribute true if this is an attribute name.
   * @return An array of three strings containing the URI part (or empty string), the local part,
   * and the raw name, all internalized, or null if there is an undeclared prefix.
   * @see org.xml.sax.helpers.NamespaceSupport2#processName
   */
  String[] processName(String qName, boolean isAttribute) {
    String name[];
    Hashtable table;

    // Select the appropriate table.
    if (isAttribute) {
      if (elementNameTable == null) {
        elementNameTable = new Hashtable();
      }
      table = elementNameTable;
    } else {
      if (attributeNameTable == null) {
        attributeNameTable = new Hashtable();
      }
      table = attributeNameTable;
    }

    // Start by looking in the cache, and
    // return immediately if the name
    // is already known in this content
    name = (String[]) table.get(qName);
    if (name != null) {
      return name;
    }

    // We haven't seen this name in this
    // context before.
    name = new String[3];
    int index = qName.indexOf(':');

    // No prefix.
    if (index == -1) {
      if (isAttribute || defaultNS == null) {
        name[0] = "";
      } else {
        name[0] = defaultNS;
      }
      name[1] = qName.intern();
      name[2] = name[1];
    }

    // Prefix
    else {
      String prefix = qName.substring(0, index);
      String local = qName.substring(index + 1);
      String uri;
      if ("".equals(prefix)) {
        uri = defaultNS;
      } else {
        uri = (String) prefixTable.get(prefix);
      }
      if (uri == null) {
        return null;
      }
      name[0] = uri;
      name[1] = local.intern();
      name[2] = qName.intern();
    }

    // Save in the cache for future use.
    table.put(name[2], name);
    tablesDirty = true;
    return name;
  }


  /**
   * Look up the URI associated with a prefix in this context.
   *
   * @param prefix The prefix to look up.
   * @return The associated Namespace URI, or null if none is declared.
   * @see org.xml.sax.helpers.NamespaceSupport2#getURI
   */
  String getURI(String prefix) {
    if ("".equals(prefix)) {
      return defaultNS;
    } else if (prefixTable == null) {
      return null;
    } else {
      return (String) prefixTable.get(prefix);
    }
  }


  /**
   * Look up one of the prefixes associated with a URI in this context.
   *
   * <p>Since many prefixes may be mapped to the same URI,
   * the return value may be unreliable.</p>
   *
   * @param uri The URI to look up.
   * @return The associated prefix, or null if none is declared.
   * @see org.xml.sax.helpers.NamespaceSupport2#getPrefix
   */
  String getPrefix(String uri) {
    if (uriTable == null) {
      return null;
    } else {
      return (String) uriTable.get(uri);
    }
  }


  /**
   * Return an enumeration of prefixes declared in this context.
   *
   * @return An enumeration of prefixes (possibly empty).
   * @see org.xml.sax.helpers.NamespaceSupport2#getDeclaredPrefixes
   */
  Enumeration getDeclaredPrefixes() {
    if (declarations == null) {
      return EMPTY_ENUMERATION;
    } else {
      return declarations.elements();
    }
  }


  /**
   * Return an enumeration of all prefixes currently in force.
   *
   * <p>The default prefix, if in force, is <em>not</em>
   * returned, and will have to be checked for separately.</p>
   *
   * @return An enumeration of prefixes (never empty).
   * @see org.xml.sax.helpers.NamespaceSupport2#getPrefixes
   */
  Enumeration getPrefixes() {
    if (prefixTable == null) {
      return EMPTY_ENUMERATION;
    } else {
      return prefixTable.keys();
    }
  }

  ////////////////////////////////////////////////////////////////
  // Internal methods.
  ////////////////////////////////////////////////////////////////

  /**
   * Copy on write for the internal tables in this context.
   *
   * <p>This class is optimized for the normal case where most
   * elements do not contain Namespace declarations. In that case,
   * the Context2 will share data structures with its parent.
   * New tables are obtained only when new declarations are issued,
   * so they can be popped off the stack.</p>
   *
   * <p> JJK: **** Alternative: each Context2 might declare
   * _only_ its local bindings, and delegate upward if not found.</p>
   */
  private void copyTables() {
    // Start by copying our parent's bindings
    prefixTable = (Hashtable) prefixTable.clone();
    uriTable = (Hashtable) uriTable.clone();

    // Replace the caches with empty ones, rather than
    // trying to determine which bindings should be flushed.
    // As far as I can tell, these caches are never actually
    // used in Xalan... More efficient to remove the whole
    // cache system? ****
    if (elementNameTable != null) {
      elementNameTable = new Hashtable();
    }
    if (attributeNameTable != null) {
      attributeNameTable = new Hashtable();
    }
    tablesDirty = true;
  }

}

// end of NamespaceSupport2.java
